<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <script src="js/demo16.js"></script>
</head>
<style>
    .btn{
        width: 100px;
        height: 50px;
    }
</style>
<body>
    <button class="btn">2秒</button>
    <button class="btn">5秒</button>
    <button class="btn">8秒</button>
    <ol id="orderList">

    </ol>
</body>
</html>